The purpose of the proposed study is to characterize changes in lipid and/or lipoprotein levels prior to the diagnosis of cancer. Data collected during the Lipid Research Clinics Coronary Primary Prevention Trial (CPPT) will be analyzed to: 1) establish the presence of a lipid lowering effect of cancer prior to its clinical detection, 2) describe the time relationship between lipid changes and cancer diagnosis, and 3) investigate the effect by tumor site, stage of clinical disease at diagnosis and tumor grade. As part of the CPPT, 3,806 healthy men, aged 35-59, with Type IIa hyperlipoproteinemia were closely followed for an average of 7.4 years of evidence of coronary heart disease. Lipid and lipoprotein determinants were made every two months throughout the trial. One hundred fourteen men developed cancer during the course of the trial. Descriptive analyses will compare the evolution of the mean lipid and lipoprotein levels between those who developed cancer and those who did not. Estimates of rates of lipid and lipoprotein change will be derived for each trial participant, either directly or by using growth curve analysis. The association between unexpectedly steep decreases in lipid and/or lipoprotein levels will be assessed using lifetable methods and proportional hazards modeling. Analyses will be repeated by tumor site, stage of clinical disease at diagnosis and tumor grade, numbers permitting. Research has shown that low cholesterol may be related to an increased incidence of cancer. Many studies have provided indirect evidence to suggest that metabolic influences of undetected cancer may explain the (observed) relationship. The proposed study will provide direct evidence of such a nascent cancer effect. In view of the public health efforts aimed at reducing population cholesterol levels, a confirmation of the existence of the nascent cancer effect is of great potential importance.